为了保证许多工作物上诸旋转面(Surfaces of Rotation)之间同心性的严格公差,一般采用了在夹持地方并无空档(Play)的夹具。现存的这一类夹具多多少少有些缺点比方说,弹簧夹头(Spring Collet)保证不了所需的精密度;有些夹具使内外表面加工并在一次校装中完成,或用丝表来校验。由於辅助时间消费甚多,从经济观点来说,又不合宜。 In order to ensure tight tolerances for concentricity between the Surfaces of Rotation on many work objects, clamps are generally used that do not play in the holding place. This type of fixture has more or less disadvantages. For example, the spring collet cannot guarantee the required precision; some fixtures make the inner and outer surfaces to be processed and completed in one school or the wire table is used for verification. . Due to the large consumption of auxiliary hours, it is not appropriate from the economic point of view.